This Perlick® Beer Faucet Lock is easy to install and remove and is tamper-proof. It has a brass tumbler and hardened steel locking hasp, and includes a key.
We bought this for our Summit kegerator simply because there are sometimes kids around. It's a very nicely made lock, and fits perfectly. It actually looks nice on the tap, in that it looks like it was made for it and doesn't look like some industrial theft-prevention device.